ELLIOTT / PATTISON CUSTOM SAILMAKERS
Capri 25 Tuning Guide
The Capri 25 rig for our sails should be set up with 10” to 12” of mast rake. This is measured by hanging a weight on the end of the main halyard and measuring how far aft of the mast it hangs at the deck level while you have just enough backstay tension to take the slack out of the backstay.
Upper shroud tension will vary slightly with crew weight, but the goal is to have the mast stay straight side to side up to the point where you start to get overpowered, about 10 knots of true wind.
I don’t think Loos Gauges are very accurate, but a good starting point is around 26 to 28 on the cap shrouds. The aft lowers will control the amount of pre-bend in your mast. For one of our mainsails we recommend 1” of pre-bend unless you are sailing with a very light crew and need a little flatter mainsail. Maximum pre-bend should be 1.5”. The forward lowers are set with just enough tension to balance against the aft lowers so that the middle of the mast stays centered. It should not fall off to leeward, or bow out to weather.
Your goal is to set the boat up for medium air, 8 to 10 knots of wind, so that when sailing the mast stays straight side to side, the mast is bent just enough to properly shape the main, and the headstay sag is right for your genoa.
Since the mast needs to be able to bend through at least a 4” range you can’t set up the rig with the lowers really tight; instead you have to rely on the combination of tension in the forward and lower shrouds to support the middle of the mast. Because of this it is very easy to have the uppers too tight, causing the middle of the mast to sag to leeward. If this happens it is better to slightly loosen the uppers so that the mast is straight even though the whole mast may fall off slightly to leeward.
Over 12 knots you should start to slightly tighten the forestay. This gives you three benefits. The backstay systems on Capri 25’s don’t allow for a long range of adjustment, from all the way off to all the way on you don’t change the length of the backstay very much, so by the time you reach a solid 12 or 13 knots you should have the backstay pulled down about as far as it will to.
By tightening the headstay as the wind builds it will give you more tension when the backstay is two blocked. Pulling the mast forward with the headstay will also make the aft lowers slightly tighter which will help to keep the mast from over bending for your main when the backstay is two blocked; and it will also move the center of effort in the mainsail slightly forward which will slightly reduce the extra weather helm you have as the wind increases.
See the table below:
UPWIND: to 6 knots 7 to 10 knots 11 to 13 knots 14 to 19 knots 20 and Up
Headsail 155% 155% 155% 140% 94%
Chainplate 6”-4” 4”-2” touching touching –
Spreaders 6”-4” 3”-2” 2”-1” 1’-0” inside 4”
Backstay loose light medium max max
Headstay set for proper rake add 1-3 turns add 4-6 turns
Boom down 2” 0 0/down2 down 2”-8” down 4”-12”
Traveller up 12” up 8”-12” up 4”-8” up 4”-down 4” played in puffs
Top Batten slight open parallel parallel slight open Twist to keep flat
The Chainplate measurement is the distance the foot of the genoa is sheeted out from the chainplate. The Spreader measurement is the distance the leech of the genoa is sheeted from the end of the spreader.